Rocket grain braking apparatus



July 9, 1957 D. D. GRIMES ROCKET GRAIN BRAKING APPARATUS 4 Sheets-Sheet l Filed June l 1955 A A BAV/D GR/MES INVENTQR.

BY f/ A WOR/VE ys IJuly 9, 1957 D. D. GRIMES 2,798,430

ROCKET GRAIN BRAKING APPARATUS BY ,Him

July 9, 1957 D. D. GRlMEs ROCKET GRAIN BRAKING APPARATUS 4 Sheets-Sheet 3 Filed June l 1955 DA VID D. GR/MES INVENTOR.

BY jam ATTORNEYS July 9, 1957 D, D, GRlMEs 2,798,430

ROCKET GRAIN BRAKING APPARATUS Filed June l, 1955 4 Sheets-Sheet 4 A um w FIG. ll.

DA V/D D. GRIMES INVENTOR.

BY Kfm@ @AMJ-*7 ATTORNEYS United States Patent .KROCKET :GRAIN BRAKusG .ABPARAaiUs A"Da x'ndl), Grimevs,;Silver Spring, Md assignorto the A'United States of ,America as represented by the Secretary of the'Navy Applicationlnne 1 1953, Serial No. `$158,928

115 Claims. (Cl. 1021-49) This Ainvention relates generally to yaerial vehicles. I'MOre .partieularlydt relates to :an `improvedbrakingap- -paratus :for preventing displacement .of .t and :possible .in- `jury,toxthefpropellent grains of asustainerrocket of a-.mis-

:sile .during :night thereof.

,'Some flight failures `of .rocket powered tmissiles ihave been traced to violent collisions ofpropellent grainsof .1the.=sustainer.rockets withzthe rear gwalls lof the rocket casings containing :.said grains. `This condition has been ifoundttofarise. during that portion of `missile ilight between booster'bur-nfoutand sustainertignition. `During the rst `part-.ofthis period, drag .forcescause amissile-to decel :erate ata Irate-.which is frequently of the `order of `tive-or sSiX :times :the acceleration due `to gravity. IUnder the sinuence of inertia ythe propellenty grains ftend to slide forward-.intthef casing, .and `if permitted to separate 4from the rear wall of said casing, they would subsequently-collide.therewith when the `commencement of4 sustainer-burningdrnparts .acceleration tothe missile. `Such collision `occurs-'.with suicient force to-rupture the `grains-or -damt age tthe casing.

.'One-of the principalobjects ofthe present invention, therefore, is 'to provide a braking `apparatus `whichlwill eliminate any `such destructive-effects caused by `inertia .byfretainingdhe propellent grains of a lrocket `powered `missileJirrnlyseated upon the rear wall of-themissile casing at Aall times `during ilight.

.A -further object `of the invention isto provide -a braking Vapparatustor usetin a rocket to retainthe propellent grains ofthe rocket seated in `their aftmost positions during rocket flight, thus preventing shifting of rsaidpropellent grainsand consequent damage to the rocket casing;

It is a further object of the invention to provide a braking apparatus having vthe foregoing features, `and whichwillbecome operative onlyunder"inertialinuences asby-the launchingofthe rocket, but at allltimes prior to launching will yremain inoperative to -permit thermalex. pansion of 4thepropellent grains.

Gther .objects and advantages of -the yinvention will be come `evident Afrom the following detailed description, taken inconjunction with the accompanying drawings, in which:

Fig l is a transverse .section -throughfthe sustainer casing of a rocket showing the braking apparatus andthepreferred locations of braking units embodying the present invention, rwith respect to said casing;

Fig. 2'is a-fragmentary axial section, on line 2--2 of Fig. l;

*Fig 3 is a sectional view of a brake unit, showing a setlback arming `mechanism used forholding said brake unit'out of operation;

Fig. 4 is aisectional view similar-toFig 3, but showing theset-iback arming mechanism in condition for permitting freemperation of the brake unit;

rrFig. -5is,a;detail perspective View vof the housingof the braketunitcshown;in Figs. 3;and 4;

F.igntisiaiplan viewlofanfelementof the brakelnnit;

r2ice zFig. .98 .is yanenlarged view in section along line IS-S 1\Fig.\9 is anenlarged sectional viev.7 along line 9-9 Fig. l0 isavviewin section of `a-moditied form ofthe ebrakingunit, asseenin thefplane ofj-line-1010 of Fig. ll;

--modiedbraking unit.

This invention generally contemplates a Vbraking ap- =paratus`particularly designed to control themovement of `Vpropellent grains ina sustainer rocket casing of a missile :under certain iflight conditions.

The apparatus employs a plurality `of braking -units `arranged `about `the casing Aaxis Yin positions 4confrontingthe-forward end portions l`of thepropellent grains.

lEachlbraking unit comprises a pair of elements mounted :sozas .to permit relative movementiin ione direction .but .tot preventsuchmovement in the `opposite direction. The :principle tif-operation of `the braking Vunit is basedupon `tthe wedgingaction ofballs or rollers in a tapered .space 1-between Ythe ytwo Imembers, the relative movements of 'which are restrictedtothoseonly ina parallel direction.

'"/When yapplied to "immobilizing the propellent grains of a rocket powered missile, `one element of the`braking `tunitis-secured` torthe forwardend ofthe rocket casing :andit-heother bears uponfa-pressure plate which'inturn is `caused by `spring means to bcarupon `the propellent 4grains.` Thearrangement issuch that theforwardmovement ofthe'pressureplate-sreStraincdbut rearward move- ;ment `4is `not. Thus, Pforward shifting of' the grains is prevented and x'the pressure fplate is in constant engagernenttherewith.

A set-backarming mechanism, 4as is `commonly ,used in f'fuze arming, may v"be `employed nto retain kthe 'braking units inoperative prior to launching of themiss'ile. 'ln `their inoperative `condition the braking units are maintainedout Vof contact with the pressure plate, thus allowing for thermal expansion of the grains. The inertial influence experienced -during launching releases the arm- Vingmechanismlwhich in turn releasesithe braking units `for operation. The braking apparatus, under the influenceof inertia,\makes -andretains contact withthepressure plate and thus, the propcllent grains to `prevent'the shifting `of said grains even under extreme conditions ot deceleration. i

`Referring Anow to the drawings `and 4in particular to Figs. fl rand 2, there ris -shown `a `portion of asustainer rocket casing 11 containing-propellent grains 12 and a forward end 4portion lfwhichtis held in place in said casing by =retaining rings 14 engaging in peripheral grooves `15 in the inner wall `of the casing. The forward end portion 1-113 is ttedwith 'an axially mounted coupling sleeve 16 `having an `inwardly directed flange 17. Inner and louter U-shaped `brackets ld and 19 the inner straddling the-outer, `areheld kin close spaced relation by screws 21; the `ends lof `the inner bracketare Welded lto the flange 17, while the ends ofthe outer brackctare suitably secured to, and thus support an. annularplate 22 constituting a part o'f the braking apparatus to 'be described in detail hereinafter. The `inner bracket 18 supports a'resonance rovd23 which Vpasses'freclythrough the bracket 19 4and axially `through the casing 1,1. `between the propellent grains 12 and terminates at the rear of said casing. 4"Such -ro ds are commonly employed in rockets lto `*prevent the break-up of the propellent `grains during burning. Thiscasing-construction permits-the accommodation fof an igniting mechanism (not shown) which forms -novpart of-the present invention. The fbraking .apparatus includes the annular plate which is provided with two diametrically opposed threaded holes 24 to mount two braking units 25 which Will be fully described hereinafter. Four recessed holes 26 symmetrically formed in the annular plate 22 each receive a anged sleeve 27 having an end Wall with a coaxial hole 28 formed therein. A bolt 29 having a head 31 and a shank 32 is contained within each sleeve 27, with said shank passing through the hole 28 in the end wall of the sleeve. The end portions of the shanks 32 are threaded and engage similarly threaded apertures 33 in an annular pressure plate 34, providing support therefor. A coil spring 35 is positioned about each of the four sleeves 27 between the annular plate 22 and the pressure plate 34 to urge said pressure plate into engagement with the propellent grains 12.

A typical braking unit is shown in detail in Figs. 3 and 4, and includes a cylindrical housing 36 having a cylindrical passage 37 extending coaxially therethrough. The housing 36 is formed at one end With an axial recess 38 of circular cross-section tapering inwardly to define a shoulder 39. A `chordal slot 41 is milled through the side Wall of the housing 36 in the region of the axial recess 38, and an annular seat 42 is `formed in the inner wall of the housing immediately below the base of said slot. Diametrically opposite the chordal slot 41 is an opening 43 through the side wall of the housing 36. An annular groove 44 is provided on the inside wall of housing 36 near the mouth of the recess 38. The purpose of the opening 43 and the groove 44 will appear hereinafter.

An inner member comprising a cylindrical sleeve 45 to be described in detail hereinafter, is slidably mounted in the passage 37 and is adapted to be fixed to the annular plate 22. That is, the upper end of the sleeve 45 is formed with a threaded hub 46 and the lower end with a transverse groove 47. When installing a braking unit a screwdriver or similar tool is inserted into the groove 47 and the threaded hub 46 is screwed into the threaded hole 24 provided in the annular plate 22.

Within the recess 38 is contained a circular ball race 48 shown in partial cutaway in Fig. 9, carrying a plurality of ball bearings 49 in annular series and which encircles the sleeve 45 in such a manner that the ball bearings 49 are caused to ride upon the outer surface of said sleeve. Above the race 48 is mounted a spring washer 51 which bears upon said race to urge it into the recess 38. A locking washer 52 to be further |described hereinafter is supported on the annular seat 42 to retain the spring washer 51 and the ball `race 48 within the recess 38, and the entire assembly is held in place by a retaining ring 53 engaging the annular groove 44.

As best seen in Figs. 6, 7 and 8, the locking washer 52 has an annular groove 54 around the inner periphery thereof for cooperation with a detent of a set back arming mechanism, to be described later, to lock the housing 36 to the sleeve 45. A chordal slot 55 is milled through the wall of the washer 52 and an opening 56 is drilled through the side wall of said washer diametrically opposite of said chordal slot. The washer 52 is positioned in the recess 38 so that the chordal slots 41 and 55 and the openings 43 and 56 are in registry. A pin 57 is iitted in the two said openings to hold the washer 52 from rotation relative to the housing 36.

The cylindrical sleeve 45 is formed with a blind lateral bore 58 which is connected by a port 59 to a longitudinal bore 61 coaxially formed in said sleeve. Slidably mounted within the longitudinal bore 61 is a bolt 62 having an axially mounted detent 63 on its inner end, said detent normally extending through the port 59 into the bore 58. A coil spring 64 is mounted in the lower end of the bore 61 and is held in place by a retaining ring 65 which is fitted in an annular groove 66 in the inner wall of said bore. The bolt 62 is further formed with a reduced lower end portion 67 which guides the upper end of the spring 64. ,An axially located, Vthreaded hole 68 is provided in the reduced portion for use in resetting the arming device, as will be described in more detail hereinafter.

At the blind end of the lateral bore 58 there is provided an opening 69 drilled through the sleeve 45 and coaxial with said bore. A bolt 71 having an axially formed stern 72, a reduced portion 73 and an intermediate portion 74, is slidably mounted within the lateral bore 58, with said stem extending through the opening 69. A coil spring 75 is mounted in the lateral bore 58 between the closed end wall thereof and the intermediate portion 74 of the bolt 71 for urging said bolt toward a retracted position. Two alined openings 76, opening into lateral bore 58 near its open end, are provided in the sleeve 45, parallel to the longitudinal axis of said sleeve, and a limit pin 77 extends diametn'cally of said bore and has its end portions fitted in said openings.

During the period of time between the installation of the braking apparatus in a missile and the launching of said missile, it is desirable to permit the free thermal ex* pansion of the propellent grains 12. To bring this about, the braking apparatus must be maintained inoperative, and a set back arming mechanism, including the bolts 62 and 71, is employed for the purpose.

The set back arming mechanism functions as follows. Prior to launching, the stem 72 of the bolt 71, as best shown in Fig. 8, is held in a position extending through the opening 69, by the detent 63, and engages the groove 54 of the locking Washer 52, thus preventing the downward movement of the housing 36 relative to the sleeve 45. In this manner the housing 36 is held out of Contact with the pressure plate 34 which bears upon the propellent grains 12, and space is thus provided in which the grains may expand.

During launching, inertial effects, produced by acceleration of the missile, cause the bolt 62 to slide downwardly `(as shown in Figs. 3 and 4) against the compression of the coil spring 64. The detent 63 is thus disengaged from the outward face of the intermediate portion 74 of the bolt 71 to release said bolt for retracting movement under the influence of coil spring 75, said retracting movement continuing until the end of the portion 73 of said bolt engages the limit pin 77. The end of the stem 72 is now disengaged from the groove 54 of locking washer 52 and the housing 36 is free to move in a downward direction to come into contact with the pressure plate 34. The same inertial effects that release the set back arming mechanism cause the housing 36 to move downwardly along the sleeve 45 until Contact is made with the pressure plate 34. It can be seen that such downward movement of the housing36 releases whatever frictional restraints are exerted by the ball bearings 49 upon the wall of the tapered recess 38 and the surface of the sleeve 45, so that free movement of said housing will be permitted.

After the housing 36 has moved to operative position in engagement with the pressure plate 34, the grains 12 will be held against forward longitudinal movement in the sustainer rocket casing 11. Any tendency of the grains to move in a forward direction toward the end portion 13 will be arrested by said pressure plate 34 in cooperation with the braking units 25. That is, a tendency of the plate 34 to move forwardly in response to pressure from the grains 12 will be arrested by action of the balls 49 which are jammed against the outer walls of the sleeves 45 by the tapered walls of the recesses 38, for locking said sleeves to their respective housings 36. It thus will be seen that the grains 12 will be protected from damage as a result of large deceleration forces brought about as a result of booster rocket burn-out.

It is desirable to test the arming mechanism of each braking unit prior to its installation in a missile by subjecting the unit to inertial set-back forces tending to release the bolts 62 and 71. To reset the arming mechanism subsequent to testing, the sleeve 45 is reinserted into the housing 36 so that the stem 72 of the bolt 71 is infregistry with the groove 54 of the locking washer 52. A threaded tool is then screwed intothe tappedhole 68 in -theflower end yof the bolt 62 andthe fdetent 63 of said bolt `is withdrawn and held fromengagement with the bolt 71 Within the lateral bore 58. A -suitable-slender tool is -inserted `through chordal grooves 41 and 550i? the housing 36 and the locking washer 52,respectively, passed on either side of the `limit ypin 77 and impressed upon the intermediate Yportion 74 of the bolt 711 `to pushlsaid boltoutwardly against the bias ofthe coil spring'75. When the stern 72 engagesthe groove 54, `the bolt 62 `is'permitted to move upward underthe influence of the coil spring-64 until the detent .63 engages lfbehind the intermediate `portion 74, whereupon the resetting `tools are lremoved andithedevice is ready'for installation.

Referring to Figs. 10, Vl1 and `1?.,.a modified form of the invention now will `be described. A cylindrical hous- 78isfformedat its upper end `with an inwardlytapering coaxial recess 79 of rectangular.cross-section. A `square passage 81, extendsfrom the center of the bottom of the recess through the housing.

A longitudinal bore 82 passescompletely `through the housing `'7d at one side of the recess 79, and a blind lateral bore `33 is formed in said housing -perpendicular to the axis of and intersecting :the-bore 382. At the inner end of said lateral-borerSS `is an\opening 84 which communicates with recess 7-9, said openingbeing in alinement with theaxis of said lateral bore. `Contained within the bores 82 and 83 is the set back arming mechanism the construction of which will-be described hereinafter.

An inner member comprising a square rod 85 is mountedrfor sliding movement in the passage S1 of the housing `78. Within the recess 79 andon each side of the rod 85' are `disposed rollers 86 which are urged-into said recess by coil springs 87 mounted aboveeach of said rollers. A circularplate 08, is tted `into a shallow circular recess 89 inthe upper endof the housing V78 and is securedby screws 91. Two pins 92 are mounted onthe underside-of theplatepSS-and extend into the recess 79 coaxial with the coil springs 87, and serve to retain said springs in operative positions with respect yto the rollers 86. The plate 88 closes the upper ends ofthelongitudinal borer82 and the recess 79, and is formed with a rectangular central opening 93 receiving the rod 85 therethrough.

`A bolt 94 is mounted for sliding movement in the bore 82. As best `seen in Fig. 12, the bolt 94has `a reduced upper end portion deiining a stop 95, and is provided with areduced, elongated shank 96. A coil spring 97 is positioned in the bore 82 about the shank A96 and is held against displacement from said bore by a retaining ring 93 and a washer 99, said ring being fitted intoagroove '1. The spring 97 urges the bolt 94 upwardly in the bore and the washer 99 provides a stop for limiting downward travel of said bolt. Mounted for sliding movement in the bore 83 is a detent element 102 having an axially disposed pin 103 on its inner end, said pin projecting through the opening 34. The detent element102 is further formed with a reducedportion defining a stop 104 on its outer end. A coil spring 105 is disposed about the pin 103 in the bore S3 and urges the -detent element outwardly and into engagement with the stop 95 of" the bolt 94. The rod 85 is formed with a recess 106 near the upper end of the lateral wall confronting the opening 84, 'to receive the pin 103for retaining saidrod and the housing 78 in locked relation. As best seen in Figs. 11 and 12, the rod 85 is formed atits upper end with a reduced, threaded shank 107 which is screwed into the plate 22.

In operation, the modified form of the invention shown in lFigs. l0, `11 `and V12 functions as follows. When installed in a missileand prior tolaunching, the housing 78 is locked to the rod'ii'S by the engagement of the pin 103 in `thelrecess 106. Under the intiuence of the coil spring 105, the bolt 102 tends to slide outwardly of the lateral bore 83 to disengage the pin 103 from the recess 106. However, the outward movement of the bolt 102 is obstructed by the stop 95 of the bolt 94 which projects, by

eyes-teo the action of the coil spring .97, into the lateral `bore 8 3 fand into Kengagement with the detent .element 102 and The inertial vforces incurred during launching cause` the A-bolt 911 to `slide downwardly until the washer 99 .is engaged,` whereupon lfurther downward sliding is prevented. The=bolt r102iinlthe1ateral .bore 83 then moves outwardlyby `the actionof the -coil spring 105, to withdraw the lpin 103 lfrom ,the recess106. Complete ejection of Ithe lbolt 102 -from 4the lateral bore A1,83`is prevented by` the stop-951of the bolt 94 'which obstructs lsaid lateral bore. VThe consequent disengagement of the ,pin 103 from the recess 106 permits the housing 7810 slide rearwardly, under set back, alongthe rod'85. The Arearward move- Amentfof thehousing '78 stops when contact is made with the pressure 4plate '34 "(,l*`i gs.2 and 4) whichlbears upon the propellent grains 12.`

Forward motionvof the housing ,78, `induced by `.inertia forces arising when lthe missile rapidly .decelerates, will tend-to restrict the rollersf86 within the vtaper of recess V79.I As pointed out in the description of the tirst embodiment, largegfrictional restraints betweenthe rollers.86 andlthe rod andthehousing 78, will arise toprevent `forward motion of said sleeve. .Consequently, the propellent Igrains 12 are held upon the rear `seat ofthe rocket casing and lshifting of said `grains with lpossible damage thereto -is prevented.

,'Accessmay be had, through the open outer end of the lateral bore 83, for resetting the set back arming mechanism after-the prefflight testing of this embodiment uo`t` -the"brake unit.

Obviously 'many modifications and variations` of the presentinvention lare possible inthe light ofthe above teachings. ltiis `therefore `to vbeuinderstood Athat within the scope ofthe appended claims the invention maybe practiced otherwise than as specifically described.

-Whatis claimed is:

1. A `braking unit "for `preventing movement of propellent grains linarocket-casing `said braking unit being supported atone :end of said casing and being arranged to engage said ,propellent grains to restrain movement thereof, said Ibraking unit consisting of fa housing having one endthereofV in engagement with said propellent grains, with its other end having a recess enlarged at one end and tapering inwardly from said enlarged` end, an inner memberhaving one end-xed'to said `casing and the other end slidable in the recess, wedging means disposed in the recess between said housing and said inner member to restrict relative movement of said inner member and sai'd housing, and detent means engaging said inner member and `housing and normally preventing relative movement of said inner member and said housing, said detent means being releasableby inertial forces upon launching of the rocket.

2. An arrangement as set forth in claim 1, `and spring means disposed within said recess to urge said wedging means into engagement with said housing andinner member to restrict relative movement of said housing and inner member in one direction.

3. `An. arrangement as set forth in claim l, wherein said Y wedging means consists of`ballbearings.

4. An arrangementas set forth in claim l, wherein said wedgingmeans consists of roller bearings.

`5. An arrangement as set forth in claim .1, wherein the recess is circular in cross-section, the inner member is a cylindrical sleeve, and the wedging means consists of ball bearings.

6. An arrangement as set forth in claim 1, wherein said recess is rectangularin cross-section, the inner member is of rectangular cross-section, and said wedging means consists of roller bearings.

7. In a rocket missile having a casing and propellent grains 'in the casing, a braking apparatus for preventing 4the shifting of said propellent grains, said apparatus com- .prising an immovable plate mounted in the forward end cluding locking means mounted on said immovable plate and adapted to engage said movable plate and to maintain it in operating position to prevent sudden forward movement of the movable plate and propellent grains.

8. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the shifting of said propellent grains, comprising a plate mounted in the forward end of the casing, and a plurality of braking units supported by said plate, said braking units being arranged to engage said propellent grains for restraining the forward movement of said propellent grains, each of said braking units including a housing having a recess enlarged at its forward end and tapering inwardly from said enlarged end, an inner member xed to said plate, said member being disposed in said recess, and wedging means disposed in said recess between said inner member and said housing to prevent movement of said housing relative t-o said inner member and restrain movement of the propellent grains.

9. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the shifting of said propellent grains, comprising an immovable plate mounted in the forward end of the casing, a movable plate supported between said immovable plate and the propellent grains, spring means urging said movable plate into engagement with the propellent grains, and braking units supported by said immovable plate for engagement with said movable plate to prevent forward movement of said movable plate, each of said lbraking units including a housing having a recess enlarged at its forward end and tapering inwardly from said enlarged end, an inner member fixed to said immovable plate, said member being slidlable in said recess, and wedging means disposed in said recess between the inner member and said housing to prevent relative movement of said housing and inner member.

10. An'arrangement as set forth in'claim 9, wherein each braking unit additionally includes detent means engaging said inner member and housingfor normally preventing relative movement of said inner member and housing, said detent means being releasable by inertial iniuences upon launching of the rocket.

11. An arrangement as set forth in claim 9, wherein each braking unit includes spring means disposed in the recess to urge the wedging means into engagement with the inner member and said housing.

l2. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the shifting of said propellent grains, comprising an immovable plate mounted in the forward end of the casing, a movable plate supported between said immovable plate and the propellent grains, spring means urging said movable plate yinto engagement with the propellent grains, and braking units supported by said immovable plate for engagement with 'said movable plate to prevent the forward movement of said movable plate, each of said braking units including-a housing having an axial passage passing therethroughand an axial recess at its forward end, said -recess tapering inwardly, a cylindrical member xed to said immovable plate and slidable in said passage, and ball bearings disposed in said recess between said housing and said member to prevent relative movement of said housing and member.

13. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the ,shifting of said propellent grains, comprising an immovable plate mounted in the forward end ofthe casing, a movable plate supported between said immovable plate and the propellent grains, spring means urging said movable plate into engagement with the propellent grains, and braking units supported by said immovable plate for engagement with said movable plate to prevent the forward movement of said movable plate, each of said braking units including a housing having a cylindrical passage therein, said passage being enlarged to define an axial recess and said recess being tapered inwardly, a cylindrical sleeve fixed to said immovable plate and slidable in the passage, set back arming means mounted in said sleeve and adapted to engage said housing to normally prevent relative movement of said housing and sleeve, said arming means being releasable frompsaid housing by inertial forces upon launching of said missile, and ball bearings disposed in said recess between said housing and sleeve to prevent relative movement of said housing and sleeve after release of said arming means.

14. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the shifting of said propellent grains, comprising an immovtable plate mounted in the forward end of the casing, a movable plate supported between said immovable plate and the propellent grains, spring means urging said movable plate into engagement with the propellent grains, and braking units supported by said immovable plate for engagement with said movable plate to prevent the forward movement of said movable plate, each of said braking units including a housing having an inwardly tapering recess at its forward end and a rectangular passage extending from the bottom of said recess through said housing, a rod of rectangular cross-section xed to said immovable plate and extending into said recess and said passage, and rollers disposed in said recess between said rod and housing to prevent relative movement of said housing and rod. n

15. In a rocket missile having a casing with propellent grains therein, a braking apparatus for preventing the shifting of said propellent grains, comprising an immovable plate mounted in the forward end of the casing, a movable plate supported between said immovable plate and the propellent grains, spring means urging said movable plate into engagement with the propellent grains, and braking units supported by said immovable plate for engagement with said movable plate to prevent the forward movement of said movable plate, each of said braking units including a housing having an inwardly tapering recess at its forward end and a rectangular passage'extending from theV bottom of said cavity through said housing, a rod of rectangular cross-section fixed to said immovable plate and extending into said recess and said passage, arming means mounted in said housing and adapted to engage said rod to prevent relative movement of said housing and rod until such time when said arming means is released as by inertial forces upon launching of said missile, and rollers disposed in said recess between said rod and housing to prevent relative movement of said housing and rod after release of said arming means.

References Cited in the le of this patent UNlTED STATES PATENTS 1,363,314 Cosgrove Dec. 28, 1920 1,963,915 Kennedy et al. June 19, 1934 2,421,266 Honger a May 27, 1947 FOREIGN PATENTS 1,008,926 France Feb. 27, 1952 

